According to the Official Mexican Standard NOM-247-SSA1-2008, the following descriptions are established for each type of product:

Whole bread: product derived from baking fermented dough, prepared by mixing whole wheat flour, whole grain cereal flour or legume flour, water, salt, sugars, edible fats, other optional ingredients, and food additives. The flour used for its preparation is obtained from milling wheat grain that retains its husk and other constituents.

Mainstream bread: It is the product resulting from baking the dough obtained by mixing fermented flour, water and salt, conditioners, and dough improvers, whether or not with edible oils and fats, milk, other ingredients, and food additives. The flour used for its preparation comes from the grinding of ripe, whole, broken, dry, and clean grain wheat, in which much of the bran and germ is removed. Everything is crushed to a grain with the proper fineness.

 Ref. http://diariooficial.gob.mx/nota_detalle.php?codigo=5100356&fecha=27/07/2009#gsc.tab=0